// Copyright (c) 2016 VMware, Inc. All Rights Reserved.
// Copyright 2017 CoreOS, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package esx

import (
	"context"
	"sync"
	"sync/atomic"
	"time"

	"github.com/vmware/govmomi/object"
	"github.com/vmware/govmomi/vim25"
)

type leaseUpdater struct {
	lease *object.HttpNfcLease

	pos   int64 // Number of bytes
	total int64 // Total number of bytes

	done chan struct{} // When lease updater should stop

	wg sync.WaitGroup // Track when update loop is done
}

func newLeaseUpdater(client *vim25.Client, lease *object.HttpNfcLease, items []ovfFileItem) *leaseUpdater {
	l := leaseUpdater{
		lease: lease,

		done: make(chan struct{}),
	}

	for _, item := range items {
		l.total += item.item.Size
		go l.waitForProgress(item)
	}

	// Kickstart update loop
	l.wg.Add(1)
	go l.run()

	return &l
}

func (l *leaseUpdater) waitForProgress(item ovfFileItem) {
	var pos, total int64

	total = item.item.Size

	for {
		select {
		case <-l.done:
			return
		case p, ok := <-item.ch:
			// Return in case of error
			if ok && p.Error() != nil {
				return
			}

			if !ok {
				// Last element on the channel, add to total
				atomic.AddInt64(&l.pos, total-pos)
				return
			}

			// Approximate progress in number of bytes
			x := int64(float32(total) * (p.Percentage() / 100.0))
			atomic.AddInt64(&l.pos, x-pos)
			pos = x
		}
	}
}

func (l *leaseUpdater) run() {
	defer l.wg.Done()

	tick := time.NewTicker(2 * time.Second)
	defer tick.Stop()

	for {
		select {
		case <-l.done:
			return
		case <-tick.C:
			// From the vim api HttpNfcLeaseProgress(percent) doc, percent ==
			// "Completion status represented as an integer in the 0-100 range."
			// Always report the current value of percent, as it will renew the
			// lease even if the value hasn't changed or is 0.
			percent := int32(float32(100*atomic.LoadInt64(&l.pos)) / float32(l.total))
			err := l.lease.HttpNfcLeaseProgress(context.TODO(), percent)
			if err != nil {
				plog.Debugf("from lease updater: %s\n", err)
			}
		}
	}
}

func (l *leaseUpdater) Done() {
	close(l.done)
	l.wg.Wait()
}
